Aerosol-generating article with narrow hollow tubular filter

ABSTRACT

An aerosol-generating article is provided, including: a substrate portion containing aerosol-forming substrate; and a hollow tubular filter portion having an inner diameter of between 0.5 millimeters and 2 millimeters, and the aerosol-forming substrate including at least one aerosol-former selected from the group consisting of: polyhydric alcohols, esters of polyhydric alcohols, and aliphatic esters of mono-, di-, or polycarboxylic acids. A system for generating an aerosol is also provided, including an aerosol-generating device including a heating chamber and a heating element; and the aerosol-generating article, the aerosol-generating article being configured to be insertable into the heating chamber.

The present invention relates to an aerosol-generating articlecomprising a substrate portion containing aerosol-forming substrate anda hollow tubular filter portion.

It is known to provide an aerosol-generating device for generating aninhalable aerosol. Such devices may heat aerosol-forming substratecontained in an aerosol-generating article without burning theaerosol-forming substrate. The aerosol-generating article may have a rodshape for insertion of the aerosol-generating article into a heatingchamber of the aerosol-generating device. A heating element may bearranged in or around the heating chamber for heating theaerosol-forming substrate once the aerosol-generating article isinserted into the heating chamber of the aerosol-generating device. Themouthpiece may be provided at the end of the aerosol-generating article.

Known aerosol-generating articles are relatively complex and requiremultiple different portions such as a substrate portion, one or morefilter portion and a cooling section for generating the inhalableaerosol, frequently requiring three to five segments or plugs in theaerosol-generating article that all need to be arranged into a rodshaped form. This requires complex making machinery and combiningmachinery.

It would be desirable to have an aerosol-generating article and amouthpiece with reduced complexity. It would be further desirable thatsuch an aerosol-generating article shows good aerosol generationcharacteristics.

According to a first aspect of the invention there is provided anaerosol-generating article comprising a substrate portion containingaerosol-forming substrate and a hollow tubular filter portion. Thehollow tubular filter portion may have an inner diameter of below 5millimeters.

A diameter of below 5 millimeters can have at least two distinctadvantages. Where the diameter is between about 2 millimeters and 5millimeters, a cavity is created at the downstream end of theaerosol-forming substrate. When the stream of material that is releasedfrom the aerosol-former substrate enters such an open space of thehollow tubular filter portion, this expansion cools down the stream tosome extent and can aerosol droplets may form. In addition, this effectcan be further enhanced to use a further reduction of diameterdownstream of the cavity, for example with a mouthpiece as will bediscussed further below.

However, it has been found that advantageously, the inner diameter ofthe hollow tubular filter portion is below 2 millimeters. At 2millimeters or below, the inner diameter of the hollow tubular filterportion is smaller than the inner diameter of conventional hollowtubular filter portions of conventional aerosol-generating articles.Advantageously, this relatively small diameter may enable a venturieffect when combined with a subsequence structure with a larger diametersuch as a further mouthpiece described below. Hence, the complexity ofthe aerosol-generating article may be reduced due to the fact that thenumber of elements of the aerosol-generating article may beadvantageously reduced such as, for example, a cooling section forgenerating the aerosol. According to the invention, some of thefunctionality of the aerosol generating article can be transferred intothe reusable mouthpiece. This means that elements that would beotherwise only used once can now be used multiple times. This means thatthe aerosol-generating articles can be simplified. This reduces theamount of waste from the single use articles that would be createdotherwise.

Additionally, this relatively small diameter may result in a desiredresistance to draw.

As used herein, the terms ‘upstream’ and ‘downstream’ are used todescribe the relative positions of components, or portions ofcomponents, of the mouthpiece and the aerosol-generating articleaccording to the invention in relation to the direction of air drawnthrough the mouthpiece and the aerosol-generating article during usethereof.

The hollow tubular filter portion of the aerosol-generating article maycomprise for example a hollow acetate tube (HAT), a fine hollow acetatetube (FHAT) or a plug of tow wrapped around a central cardboard tube,all of which structures being known from manufacture of filter elements.The hollow tubular filter portion preferably comprises a hollow centralspace. The inner diameter of the hollow tubular filter portion may referto the diameter of the hollow central space.

The hollow tubular filter portion may be located immediately downstreamof the substrate portion containing the aerosol-forming substrate of theaerosol-generating article and may directly abut the aerosol-formingsubstrate. The aerosol-generating article may only comprise thesubstrate portion and the hollow tubular filter portion.

If desired or required, for example to achieve a sufficiently highresistance to draw of the aerosol-generating article, an additionalfilter section may be included in the aerosol-generating article.Preferably such additional filter section may be included between thesubstrate portion and the hollow tubular filter portion. Preferably,such additional filter section comprises a filtration material such as,for example, cellulose acetate. Preferably, the length of the additionalfilter section is between about 4 millimeters and about 8 millimeters,preferably, between about 5 millimeters and about 7 millimeters.Preferably, the combined length of the additional filter section and thehollow tubular filter portion is between about 10 millimeters and about18 millimeters, preferably, 13 millimeters.

The hollow tubular filter portion may be formed from any suitablematerial or combination of materials. For example, the hollow tubularfilter portion may be formed from one or more materials selected fromthe group consisting of: cellulose acetate; cardboard; paper, such ascrimped heat resistant paper or crimped parchment paper; cotton;viscose; glass fibres; and other polymeric materials, such as lowdensity polyethylene (LDPE). In a preferred embodiment, the hollowtubular filter portion is formed from cellulose acetate.

The hollow tubular filter portion preferably has an external diameterthat is approximately equal to the external diameter of theaerosol-generating article. The hollow tubular filter portion may havean external diameter of between approximately 4 millimeters andapproximately 8 millimeters, for example of between approximately 5millimeters and approximately 6 millimeters, preferably around 5.3millimeters. The hollow tubular filter portion may have a length ofbetween approximately 10 millimeters and approximately 14 millimeters.

The hollow tubular filter portion may have an inner diameter of between0.5 millimeters and 2 millimeters, preferably between 0.75 millimetersand 1.25 millimeters, more preferably around 1 millimeter.Alternatively, the hollow tubular filter portion may have an innerdiameter between 2 millimeters and 5 millimeters.

The aerosol-generating article may comprise a cylindrical filter portionarranged between the substrate portion and the hollow tubular filterportion.

The cylindrical filter portion may prevent aerosol-forming substratesuch as tobacco from entering the hollow tubular filter portion, whichmay clog the hollow tubular filter portion. The cylindrical filterportion may further aid in removing unwanted constituents from the aircontaining vaporized aerosol-forming substrate drawn through theaerosol-generating article. Additionally, the cylindrical filter portionmay be used to adjust the resistance to draw to a desired level. In casea cylindrical filter portion is provided, the total length of thecylindrical filter portion plus the hollow tubular filter portion may bebetween 10 millimeters and 13 millimeters. The cylindrical filterportion may have a length between 4 millimeters and 8 millimeters,preferably between 5 millimeters and 7 millimeters. According to thisaspect, the hollow tubular filter portion may have a length between 5millimeters and 9 millimeters. Most preferred the combined length of thecylindrical filter portion and the hollow tubular filter portion is 13millimeters.

The invention also relates to a system comprising an aerosol-generatingarticle as described above and a mouthpiece configured attachable to theaerosol-generating article. The aerosol-generating article with a hollowtubular filter portion with small diameter in conjunction with themouthpiece may reduce complexity of the system as well as improveaerosol generation. The mouthpiece preferably is provided as a reusablemouthpiece.

The mouthpiece may comprise an upstream end with a cavity configured forenabling insertion of the aerosol-generating article into the cavity.

The cavity may be configured for securely holding the aerosol-generatingarticle in the cavity and thus in connection with the mouthpiece. Thecavity may be configured to tightly receive the aerosol-generatingarticle so as to prevent leakage of one or more of air, vaporizedaerosol-forming substrate and aerosol between the aerosol-generatingarticle and the mouthpiece. A user may insert the aerosol-generatingarticle into the cavity of the mouthpiece for usage. After the smokingexperience, the user may remove the used aerosol-generating article fromthe cavity and insert a new aerosol-generating article into the cavity.

The cavity may comprise a conical section at a downstream side of thecavity, wherein an inner diameter of the cavity may decrease in theconical section in a downstream direction.

The conical section may be provided to reduce the diameter of the cavityso that an inserted aerosol-generating article is tightly received atthe downstream end of the cavity. Preferably, the conical section isprovided to contact the outer perimeter of the aerosol-generatingarticle during insertion of the aerosol-generating article. The conicalsection may thus provide a tight connection between the downstream endof the conical section and the outer perimeter of the aerosol-generatingarticle, thereby facilitating secure holding of the aerosol-generatingarticle. Furthermore, a seal may be provided by the downstream end ofthe conical section to prevent escape of one or more of air, vaporizedaerosol-forming substrate and aerosol between the aerosol-generatingarticle and the mouthpiece, after the aerosol-generating article hasbeen inserted into the cavity of the mouthpiece.

The inner diameter of the cavity adjacent the upstream end of themouthpiece may be larger than the outer diameter of theaerosol-generating article. This diameter may ease insertion of theaerosol-generating article.

A minimum inner diameter of the conical section may be smaller than anouter diameter of the aerosol-generating article. In embodiments of theinvention where the inner diameter of the hollow tubular filter portionis between 2 millimeters and 5 millimeters, the mouthpiece preferablycomprises a reduction of its inner diameter to between about 0.7 and 1.5millimeters. Such a reduction of the inner diameter of the mouthpiecemay to create the pin-hole effect that helps determining the aerosol.Such a reduction of the inner diameter of the mouthpiece may alsocontribute to a target resistance to draw of the aerosol-generatingarticle.

Preferably, the minimum inner diameter of the conical section is reachedat the downstream end of the cavity, more preferably at the downstreamend of the conical section of the cavity. During insertion of theaerosol-generating article, the outer perimeter of theaerosol-generating article may come into contact with the inner wall ofthe cavity so that the outer perimeter of the aerosol-generating articlemay be squeezed together during insertion of the aerosol-generatingarticle into the cavity of the mouthpiece.

The mouthpiece may comprise a stop configured for limiting insertion ofthe aerosol-generating article into the cavity.

The stop may be provided at the downstream end of the cavity. The stopmay be configured as a wall that extends essentially perpendicular tothe longitudinal axis of the mouthpiece. The stop may comprise a sealingelement such as an 0-ring.

The mouthpiece may comprise a downstream end and a venturi sectionextending from the downstream end in an upstream direction.

The mouthpiece may comprise a central airflow channel. The centralairflow channel may be shaped to form the venturi section. The centralairflow channel may be arranged along the longitudinal axis of themouthpiece so that, after insertion of the hollow tubular filter portionof the aerosol-generating article into the cavity of the mouthpiece, thelongitudinal axis of the aerosol-generating article may align with thelongitudinal axis of the mouthpiece. In other words, after connectingthe aerosol-generating article to the mouthpiece, the central airflowchannel of the mouthpiece may be aligned with the aerosol-generatingarticle such that air may be drawn through the aerosol-generatingarticle and into the central channel of the mouthpiece. When anaerosol-generating article is inserted into the cavity of themouthpiece, the venturi section may directly abut the aerosol-generatingarticle.

The venturi section may be conical, wherein an inner diameter of theventuri section increases towards the downstream end of the mouthpiece.Where a pin-hole type constriction of the inner diameter of themouthpiece is present, the conical section is arranged adjacent anddownstream of that constriction of the inner diameter of the mouthpiece.An optimized Venturi effect may be realized by the small diameter in thehollow tubular filter portion of the aerosol-generating article indirect abutment with the venturi section. Air flowing through theaerosol-generating article and particularly the substrate portion of theaerosol-generating article in a downstream direction will enter thesmall diameter hollow tubular filter portion. After passing the hollowtubular filter portion, the air containing vaporized aerosol-formingsubstrate will stream into the venturi section and expand after theconstriction (either constricted by the small inner diameter of thehollow tubular filter section or constriction in the mouthpiece). As areaction, the air will cool and aerosol droplets will form in the air.Hence, by providing an aerosol-generating article with a hollow tubularfilter portion at the downstream end with a small inner diameter and amouthpiece with a venturi section in direct abutment to the hollowtubular filter portion, a simple aerosol-generating article may beprovided with optimized aerosol generation in the venturi section of themouthpiece.

A conical angle of the venturi section may be between 0 degrees to 20degrees, preferably between 4 degrees to 10 degrees, more preferablyaround 6 degrees. The conical angle may be measured between thelongitudinal axis of the mouthpiece and an angled inner wall of theventuri section.

The maximum inner diameter of the venturi section of the mouthpiece andthe inner diameter of the hollow tubular filter portion of theaerosol-generating article may be configured such that air containingvaporized aerosol-forming substrate being drawn from the hollow tubularfilter portion into the venturi section may be subject to a temperaturedrop. The initial temperature may be around 250 degrees Celsius. Thetemperature drop may be between 50 degrees Celsius and 150 degreesCelsius, preferably between 75 degrees Celsius and 125 degrees Celsius,more preferably around 100 degrees Celsius. The temperature may drop toaround 160 degrees Celsius. The temperature may further decrease towardsthe downstream end of the venturi section. Aerosol may thus form in theventuri section. The temperature may be, at the downstream end of theventuri section, between 40 degrees Celsius to 70 degrees Celsius,preferably between 50 degrees Celsius and 60 degrees Celsius.

The airflow channel of the mouthpiece may have a minimum diameter thatis larger than the inner diameter of the hollow tubular filter portionof the aerosol-generating article.

In this way, it is guaranteed that the air will expand in the venturisection when flowing into the venturi section from the hollow tubularfilter portion and that thereby aerosol will be generated.

The minimum diameter of the airflow channel may be at least 2millimeters, preferably at least 3 millimeters, more preferably at least4 millimeters. To enable expansion of the air entering the venturisection from the hollow tubular filter portion, the minimum diameter ofthe venturi section is equal to or larger than the inner diameter of thehollow tubular filter portion. The minimum diameter of the venturisection may be 1 millimeters larger, preferably 2 millimeters larger,most preferred 3 millimeters larger than the inner diameter of thehollow tubular filter portion.

As used herein, the term ‘aerosol-generating article’ refers to anarticle comprising an aerosol-forming substrate that is capable ofreleasing volatile compounds that can form an aerosol, typically underthe application of heat, that is, above room temperature. Theaerosol-generating article may be disposable.

The aerosol-generating article may be substantially cylindrical inshape. However, alternatively other cross sections may be used. Indeed,the cross section of the aerosol-generating article may vary along itslength, for example by varying the shape of the cross section or thecross sectional dimensions. The aerosol-generating article may besubstantially elongate. The aerosol-generating article may have a lengthand a circumference substantially perpendicular to the length. Theaerosol-forming substrate may be substantially cylindrical in shape. Theaerosol-forming substrate may be substantially elongate. Theaerosol-forming substrate may also have a length and a circumferencesubstantially perpendicular to the length.

The aerosol-generating article may have a total length between 30millimeters and 60 millimeters, preferably between 40 millimeters and 50millimeters, more preferably 45 millimeters. The aerosol-generatingarticle may have an external diameter between approximately 4millimeters and 8 millimeters, preferably between 5 millimeters and 6millimeters, more preferably around 5.3 millimeters. In one embodiment,the aerosol-generating article has a total length of approximately 45millimeters. Further, the aerosol-forming substrate may have a length ofbetween 20 millimeters and 55 millimeters. The aerosol-generatingarticle may comprise an outer wrapper, preferably an outer paperwrapper.

As used herein, the term ‘aerosol-forming substrate’ relates to asubstrate capable of releasing volatile compounds that can form anaerosol. Such volatile compounds may be released by heating theaerosol-forming substrate. An aerosol-forming substrate may convenientlybe part of the aerosol-generating article or smoking article.

The aerosol-forming substrate is a substrate capable of releasingvolatile compounds that can form an aerosol. The volatile compounds maybe released by heating the aerosol-forming substrate. Theaerosol-forming substrate may comprise nicotine. The aerosol-formingsubstrate may comprise plant-based material. The aerosol-formingsubstrate may comprise tobacco. The aerosol-forming substrate maycomprise a tobacco-containing material containing volatile tobaccoflavour compounds, which are released from the aerosol-forming substrateupon heating. The aerosol-forming substrate may alternatively comprise anon-tobacco-containing material. The aerosol-forming substrate maycomprise homogenised plant-based material, including homogenizedtobacco, for example made by, for example, a paper making process or acasting process.

The aerosol-forming substrate may comprise at least one aerosol-former.An aerosol-former is any suitable known compound or mixture of compoundsthat, in use, facilitates formation of a dense and stable aerosol andthat is substantially resistant to thermal degradation at thetemperature of operation of the system. Suitable aerosol-formers are forexample: polyhydric alcohols, such as triethylene glycol, 1,3-butanedioland glycerine; esters of polyhydric alcohols, such as glycerol mono-,di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylicacids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.Aerosol formers may be polyhydric alcohols or mixtures thereof, such astriethylene glycol, 1,3-butanediol and glycerine. The aerosol-former maybe propylene glycol. The aerosol former may comprise both glycerine andpropylene glycol.

The invention further relates to an aerosol-generating device comprisinga mouthpiece as described herein. The aerosol-generating device maycomprise a housing, electric circuitry, a power supply, a heatingchamber and a heating element.

As used herein, an ‘aerosol-generating device’ relates to a device thatinteracts with an aerosol-forming substrate to generate an aerosol. Theaerosol-forming substrate may be part of the aerosol-generating article.An aerosol-generating device may be a device that interacts with anaerosol-forming substrate of the aerosol-generating article to generatean aerosol.

The electric circuitry may comprise a microprocessor, which may be aprogrammable microprocessor. The microprocessor may be part of acontroller. The electric circuitry may comprise further electroniccomponents. The electric circuitry may be configured to regulate asupply of power to the heating element. Power may be supplied to theheating element continuously following activation of the system or maybe supplied intermittently, such as on a puff-by-puff basis. The powermay be supplied to the heating element in the form of pulses ofelectrical current. The electric circuitry may be configured to monitorthe electrical resistance of the heating element, and preferably tocontrol the supply of power to the heating element dependent on theelectrical resistance of the heating element.

The device may comprise a power supply, typically a battery, within themain body. As an alternative, the power supply may be another form ofcharge storage device such as a capacitor. The power supply may requirerecharging and may have a capacity that enables to store enough energyfor one or more usage experiences; for example, the power supply mayhave sufficient capacity to continuously generate aerosol for a periodof around six minutes or for a period of a multiple of six minutes. Inanother example, the power supply may have sufficient capacity to createan aerosol for multiple puffs.

The power supply may be any suitable power supply, for example a DCvoltage source such as a battery. In one embodiment, the power supply isa Lithium-ion battery. Alternatively, the power supply may be aNickel-metal hydride battery, a Nickel cadmium battery, or a Lithiumbased battery, for example a Lithium-Cobalt, a Lithium-Iron-Phosphate,Lithium Titanate or a Lithium-Polymer battery.

The heating element may be arranged inside or around the heating chamberfor heating an aerosol-generating article insertable into the heatingchamber. The heating chamber may be a cavity. Alternatively, or inaddition, an internal heating element may be provided, for example a pinor a blade that is inserted for use at least partly into theaerosol-forming substrate.

For example, the device may include an external heating elementpositioned around a perimeter of the heating chamber. An externalheating element may take any suitable form. For example, an externalheating element may take the form of one or more flexible heating foilson a dielectric substrate, such as polyimide. The flexible heating foilscan be shaped to conform to the perimeter of the heating chamber.Alternatively, an external heating element may take the form of ametallic grid or grids, a flexible printed circuit board, a mouldedinterconnect device (MID), ceramic heating element, flexible carbonfibre heating element or may be formed using a coating technique, suchas plasma vapour deposition, on a suitable shaped substrate. An externalheating element may also be formed using a metal having a definedrelationship between temperature and resistivity. In such an exemplarydevice, the metal may be formed as a track between two layers ofsuitable insulating materials. An external heating element formed inthis manner may be used to both heat and monitor the temperature of theexternal heating element during operation. The heating element may beconfigured to heat to a temperature of around 250 degrees Celsius.

The invention also relates to a method for attaching anaerosol-generating article comprising a hollow tubular filter portionwith an inner diameter of below 5 millimeters to a mouthpiece.

Features described in relation to one aspect may equally be applied toother aspects of the invention.

The invention will be further described, by way of example only, withreference to the accompanying drawings in which:

FIG. 1 shows an aerosol-generating article comprising a hollow tubularfilter portion with a small-diameter and a mouthpiece for attachmentwith the aerosol-generating article; and

FIG. 2 shows the aerosol-generating article with attached mouthpiece aswell as an aerosol-generating device for insertion of theaerosol-generating article.

FIG. 1 shows an aerosol-generating article 10 comprising a substrateportion 12 containing aerosol-forming substrate. Downstream of thesubstrate portion 12 on the right part of the aerosol-generating article10 shown in FIG. 1, a hollow tubular filter portion 14 is provided. Thehollow tubular filter portion 14 has a hollow central space 16. Thehollow central space 16 has a relatively small inner diameter of below 2millimeters, preferably of around 1 millimeters.

The top part of FIG. 1 shows the aerosol-generating article 10 as wellas a detached mouthpiece 18. The mouthpiece 18 comprises a cavity 20 forinsertion of the aerosol-generating article 10 into the cavity 20. Thecavity 20 has an upstream end 22 facing the aerosol-generating article10. The upstream end 22 of the cavity 20 has a diameter which is largerthan the outer diameter of the aerosol-generating article 10 such thatthe aerosol-generating article 10 can easily be inserted into the cavity20. The cavity 20 has a conical section 24 at a downstream end 26 of thecavity 20 such that the aerosol-generating article 10 inserted into thecavity 20 is compressed and thus tightly received in the cavity 20 oncefully inserted into the cavity 20. At a downstream end 26 of the cavity20, the cavity 20 comprises a stop 28 to prevent over insertion of theaerosol-generating article 10.

The bottom part of FIG. 2 shows the aerosol-generating article 10attached with the mouthpiece 18 after insertion of theaerosol-generating article 10 into the cavity 20 of the mouthpiece 18.

FIG. 2 shows the aerosol-generating article 10 connected with themouthpiece 18 and in addition an aerosol-generating device 30. In theleft part of FIG. 2, the aerosol-generating article 10 has been insertedinto the cavity 20 of the mouthpiece 18 thereby establishing aconnection between the aerosol-generating article 10 and the mouthpiece18. However, the aerosol-generating article 10 and the mouthpiece 18 arenot yet inserted into the aerosol-generating device 30. In the rightpart of FIG. 2, the aerosol-generating article 10 is inserted into theaerosol-generating device 30.

The aerosol-generating device 30 comprises a heating chamber 32 forinsertion of the aerosol-generating article 10. A heating element 34 isarranged in or surrounding the heating chamber 32 for heating theaerosol-forming substrate contained in the aerosol-generating article 10for generating an inhalable aerosol. The aerosol-generating device 30may comprise further components such as a power supply 36 for supplyingelectrical energy to the heating element 34 as well as electriccircuitry 38 for controlling the supply of electrical energy from thepower supply 36 to the heating element 34.

The right part of FIG. 2 shows the mouthpiece 18 not in directattachment with the aerosol-generating device 30. However, if desired,upon insertion of the aerosol-generating article 10 into theaerosol-generating device 30, the mouthpiece 18 may contact theaerosol-generating device 30 so that the aerosol-generating article 10may be fully surrounded by the heating chamber 32 of theaerosol-generating device 30 as well as the mouthpiece 18. In this way,air may be prevented from entering or exiting between the mouthpiece 18and the aerosol-generating device 30. In such a configuration, theaerosol-generating device 30 preferably comprises an air inlet forenabling ambient air to enter the heating chamber 32. When a user puffson the mouthpiece 18, air is preferably drawn from the ambient airthrough the air inlet into the heating chamber 32 and further throughthe aerosol-generating article 10 towards the mouthpiece 18 and a mouthof a user.

Alternatively, a gap may be provided between the mouthpiece 18 and theaerosol-generating device 30 as shown in FIG. 2 so as to enableadditional airflow into the aerosol generating device. As a furtheralternative, the aerosol-generating article 10 may be wrapped with awrapper which essentially prevents air from entering or exiting theinner of the aerosol-generating article 10 from/to the outside throughthe wrapper even if a gap is provided between the mouthpiece 18 and theaerosol-generating device 30. Hence, a gap may be provided between themouthpiece 18 and the aerosol-generating device 30, while air is limitedto substantially flow only through the aerosol-generating article 10along the longitudinal axis of the aerosol-generating article 10.

The mouthpiece 18 shown in FIGS. 1 and 2 comprises a venturi section 40,and the inner diameter of the venturi section 40 increases towards thedownward end of the mouthpiece 18. Together with the small-diameter ofthe hollow tubular filter portion 14 of the aerosol-generating article10, optimized aerosol may be generated in the mouthpiece 18. In thisregard, the inner diameter of the hollow tubular filter portion 14 issmaller than the smallest inner diameter of the venturi section 40 ofthe mouthpiece 18. Hence, if air containing vaporized aerosol-formingsubstrate flows from the aerosol-generating article 10, more preciselythe hollow tubular filter portion 14 of the aerosol-generating article10, to the mouthpiece 18, the air expands and cools down so that aerosoldroplets can form.

1.-10. (canceled)
 11. An aerosol-generating article, comprising: asubstrate portion containing aerosol-forming substrate; and a hollowtubular filter portion, wherein the hollow tubular filter portion has aninner diameter of between 0.5 millimeters and 2 millimeters, and whereinthe aerosol-forming substrate comprises at least one aerosol-formerselected from the group consisting of: polyhydric alcohols, esters ofpolyhydric alcohols, and aliphatic esters of mono-, di-, orpolycarboxylic acids.
 12. The aerosol-generating article according toclaim 11, wherein the at least one aerosol-former comprises at least onepolyhydric alcohol.
 13. The aerosol-generating article according toclaim 11, wherein the at least one aerosol-former comprises triethyleneglycol, 1,3-butanediol, or glycerine.
 14. The aerosol-generating articleaccording to claim 11, wherein the hollow tubular filter portion has aninner diameter of between 0.75 millimeters and 1.25 millimeters.
 15. Theaerosol-generating article according to claim 11, wherein the hollowtubular filter portion has an inner diameter of around 1 millimeter. 16.The aerosol-generating article according to claim 11, wherein the hollowtubular filter portion has an external diameter of between approximately4 millimeters and approximately 8 millimeters.
 17. Theaerosol-generating article according to claim 11, wherein the hollowtubular filter portion has an external diameter of between approximately5 millimeters and approximately 6 millimeters.
 18. Theaerosol-generating article according to claim 11, wherein the hollowtubular filter portion is a hollow acetate tube.
 19. Theaerosol-generating article according to claim 11, wherein the hollowtubular filter portion is located downstream of the substrate portion.20. The aerosol-generating article according to claim 19, wherein thehollow tubular filter portion directly abuts the aerosol-formingsubstrate.
 21. The aerosol-generating article according to claim 11,further comprising a cylindrical filter portion arranged between thesubstrate portion and the hollow tubular filter portion.
 22. A systemfor generating an aerosol, comprising: an aerosol-generating deviceincluding a heating chamber and a heating element; and anaerosol-generating article according to claim 11, wherein theaerosol-generating article is configured to be insertable into theheating chamber.
 23. The system for generating an aerosol according toclaim 22, wherein the heating element comprises an external heatingelement positioned around a perimeter of the heating chamber.